gsminmag Mineralogical Magazine Mineralogical Magazine 0026-461X Mineralogical Society 10.1180/minmag.1960.032.248.07 Two Synthetic Compounds Containing Chromium in Different Valency States Johnson W. M.A. The United Steel Companies Limited, Research and Development Dept., Swinden Laboratories, Moorgate, Rotherham, Yorkshire. 3 1960 32 248 408 411 Copyright © 1960, The Mineralogical Society 1960 Summary

Two compounds, one an apatite and the other a perovskite, have been synthesized by sintering mixtures containing CaO and Cr2O3, and CaO, Cr2O3, and Fe2O3 respectively. The apatite formed by partial oxidation of the Cr2O3 and subsequent pick-up of moisture from the atmosphere, to give Ca5(CrO4)3OH. The perov-skite formed as a non-stoicheiometric compound Ca4(Fe,Cr)4O11 by partial oxidation of the Cr2O3 during firing. Lattice parameters and interplanar spacings are given for the two structures.